1. Field of the Invention
This invention relates to cabinet constructions for refrigeration apparatus, and more specifically, to the provision of means in such cabinets to provide thermal stress relief to avoid thermal stress cracking of cabinet components.
2. Background Art
Prior art of possible relevance includes the following U.S. Pat. Nos. 2,876,927 issued Mar. 10, 1959 to Henning; 3,363,796 issued Jan. 16, 1968 to Pringle; 3,406,858 issued Oct. 22, 1968 to Jackson; 3,813,137 issued May 28, 1974 to Fellwock et al; 3,858,409 issued Jan. 7, 1975 to Besing; 3,940,195 issued Feb. 24, 1976 to Tillman; and 3,944,111 issued Mar. 16, 1976 to Nonomaque et al.
The last several years have seen a considerable advancement in the art of insulation for refrigeration apparatus in terms of the increasing use of foamed-in-place insulation using, as for example, rigid polyurethane foam. Relatively thin layers of such foam provide excellent insulation and as a consequence, refrigerating equipment such as refrigerators, freezers, and refrigerator-freezer combinations, have been made with relatively small exterior cabinet dimensions as compared to their internal storage capacity.
Typically, an exterior cabinet is formed of metal and the storage space is defined by a thermoplastic liner of one piece construction received within the metal cabinet and spaced therefrom to define an insulating space receiving the foam. The foam and the plastic have different coefficients of thermal expansion and, inasmuch as typical insulating foams employed bond to the plastic liner, when the refrigerating apparatus is subjected to extreme temperature changes the respective thermal forces of expansion and contraction involved can cause the thermoplastic liner to crack, break or otherwise be damaged. Consequently, considerable care must be taken to avoid constructions wherein thermal stress buildup is sufficient to cause such damage. A number of the above-identified patents describe and illustrate approaches which seek to minimize a thermal stress problem, and the present invention is directed to overcoming a thermal stress problem.